This invention relates generally to trunked radio communication systems and conventional dispatch radio systems and is more particularly directed to an interface circuit for interfacing a console to a trunked radio system.
Trunked radio systems have developed as a means of providing increased mobile unit capacity in systems which operate in a fixed geographic area. Trunked communication systems employ the sharing of a limited number of communication channels (repeaters) with a large number of subscriber units. Accordingly, no repeater is dedicated to the sole use of a specific subscriber unit or group of units. The channel resources are dynamically allocated to satisfy the current communication demands of the subscriber units. Typically, a subscriber unit is a mobile vehicle such as a taxicab, construction company, or individuals who desire vehicular communication. In many of these situations, it is desirable to have a home or base dispatcher communicate with the several mobile units in the field. However, prior art systems have treated the dispatcher as simply another subscriber unit. Accordingly, once a call was established, the dispatcher could not be assured of being heard over the other subscribers units. Thus, prior art trunked systems suffered a severe disadvantage which limited their utility in several public service applications since dispatcher takeover capability could not be guaranteed.
Control consoles have been interfaced to conventional channel communication systems in the past. In a conventional channel system, each unit is constrained to operate only on a predetermined channel. Accordingly, since communication with a particular unit could only take place through a predetermined repeater, the console was typically hard-wired to the repeaters to control all of its functions. Thus, the console operator, when selecting a group with which to communicate, controls the function of the repeater on which the group resides. The conventional channel communication systems, as compared to a trunked communication system, suffers the detriment of being spectrally inefficient since the channel remains idle unless a particular unit is communicating during any particular time. Further, the capacity of a particular group may be limited, in that, since all units are required to remain on same channel, if a first group grows to exceed the capacity of the channel, the units are not easily transferred to a second channel to spread the communication demand across the available channels. Therefore, while trunked systems suffer the detriment of lacking full console control, they are more spectrally efficient and more easily accommodate the dynamically varying communication channel demands of its subscriber units.
The present invention combines the advantages of console control with that of trunked radio systems. A unique interface and signalling protocol provide communications between a console which is constructed and arranged to provide the trunking data information, on a time division multiplexed arrangement, between several dispatchers. Thus, an improved trunked communication system is afforded by the present invention providing increased flexibility and utility in several communication markets.